Factories and other industrial environments are increasingly using remote devices (ex. video cameras, sensors, control devices, etc.) for control, monitoring, or other functions in their manufacturing equipment. Among other operations, these devices may be used to monitor activities for real-time or recorded operations or to control specific processes or equipment. They may be located in a wide range of static or mobile locations in the industrial facility and may require DC (Direct Current) or AC (Alternate Current) power to function and/or an ability to receive data (ex. instructions) from a distant location and/or an ability to transmit data (ex. video content) to a distant location.
Due to the remote locations and/or movement of these devices, it is not typically convenient to plug in the devices to local power outlets. Further, due to electromagnetic interference that is typical within industrial environments, wireless communication technologies may not provide a reliable communication channel. Further, in the case that there are a large number of these remote devices, the cost for adding wireless receivers/transmitters within each device can be high.
Most industrial environments employ the use of wired solutions to power and communicate to/from the remote devices. In many cases, cables spooled on rotatable reels are used to connect to the remote devices and control the extracting and retracting of the cable, thus reducing the risk of cables getting tangled or caught within equipment. One significant issue with using cables spooled on rotatable reels is how to transfer electrical current onto the cable when the cable is connected to an element on the reel that is rotating relative to a static power source. Another significant issue is how to transfer data to/from remote devices through the cable when the cable is connected to an element on the reel that is rotating relative to a static data receiver and/or transmitter.
In one implementation, to enable transfer of electrical power, the rotatable element within the reel that is connected to one end of the cable comprises one or more copper brushes. These brushes may come into contact with a static frame of the reel as the rotatable element rotates and can provide a continuous or semi-continuous electrical connection between the static frame of the reel and the rotatable element that the cable is connected to. Electrical power can be transferred through these copper brushes from the static frame to the rotatable element and can allow for electrical power to be transferred to remote devices connected to the rotatable element via the cable. A problem with this implementation is that the copper brushes have been shown to wear down and the continuous surface-on-surface friction is a significant source of failures for a wide variety of reasons including carbon buildup causing false contact, broken brushes and generation of heat. To overcome these problems with using copper brushes to transfer electrical power to the rotatable element, in some implementations thicker copper is used or gold alloy brushes replace the copper brushes. These solutions come at a significantly increased cost and have many of the same problems since they still rely on surface-to-surface friction to transfer the electrical power. An additional problem is that brushes, although suited to transfer DC power, cause significant electromagnetic noise and interference to any data being transferred either on themselves or on nearby lines.
Another implementation of a reel is disclosed within U.S. Pat. No. 3,430,179 issued Feb. 25, 1969 and entitled “Cable Reel” by Shoji, herein incorporated by reference. In this implementation, an electrical connector for connecting a multiconductor cable on a reel with an exterior multiconductor cable comprises a rotatable inner sleeve and a stationary outer sleeve, and a one-piece, flat flexible multiconductor element (commonly known as ribbon-cable or ribbon-wire or flat flex cable) wound around the inner sleeve. The inner end of the multiconductor element terminates at a multiple terminal electrical connector secured to the inner sleeve, and the outer end of the cable terminates at a multiple terminal electrical connector secured to the outer sleeve. The inner sleeve is rotatable with the reel, and the multiconductor element unwinds from the inner sleeve as the reel revolves and the multiconductor cable on the reel is payed out. In this implementation, data can be transferred along the multiconductor element. One problem with this solution is that the multiconductor element when wound around the inner sleeve can generate self-inductance and high distributed capacitance that can limit the bandwidth of data that can be communicated through the multiconductor element.
Against this background, there is a need for solutions that will mitigate at least one of the above problems. In particular, there is a need for a cable reel that has an improved apparatus for power and/or data communication transfer to/from a cable on the reel.